Klebsiella, Enterobacter, and Serratia Infections

The gram-negative bacteria Klebsiella, Enterobacter, and Serratia are closely related normal intestinal flora that rarely cause disease in immunocompetent hosts. Diagnosis is by culture. Treatment is with antibiotics.

Klebsiella, Enterobacter, and Serratia are members of the Enterobacterales (formerly Enterobacteriaceae) family.

Infections with these 3 bacteria are often hospital-acquired and occur mainly in patients with diminished resistance to infection (eg, underlying medical conditions, indwelling catheters and devices). These bacteria can cause a wide variety of infections, including bacteremia, surgical site infections, intravascular catheter infections, and respiratory or urinary tract infections that manifest as pneumonia, cystitis, or pyelonephritis and that may progress to lung abscess, empyema, bacteremia, and sepsis, as in the following:

• Klebsiella pneumonia, a rare and severe disease often with dark brown or red currant–jelly sputum, lung abscess formation, and empyema, is most common among people with diabetes and people with alcohol use disorder. It can also cause primary community-acquired liver abscess.

• Serratia, particularly S. marcescens, has greater affinity for the urinary tract but also is frequently isolated from the respiratory tract and wounds.

• Enterobacter most often cause nosocomial infections (respiratory, urinary, and bloodstream) but can cause otitis media, cellulitis, and neonatal sepsis.

Diagnosis is by culture of blood and/or other infected tissue or fluid collections. Susceptibility testing is also done.